The present invention relates to a crawler unit for coupling to a wheelchair, and especially to a unit for climbing stairs and travelling up access ramps, wherein a crawler unit undercarriage which comprises the power-driven tracks and fits between the main wheels of the wheelchair includes an adapter for securing the wheelchair in a rearwardly tilted travelling position, in which the wheels of the wheelchair are lifted off the ground.
Such a combination of wheelchair and crawler unit offers the advantage that the coupling between the two elements is only effected as required and the user of the wheelchair is able to use the wheelchair by him. The wheelchair user need not leave the wheelchair when the crawler unit is coupled or decoupled, respectively. Advantageously, crawler units with tracks having a strong tread pattern and made from rubber or rubber-like plastic material are employed, wherein two tracks are provided which are adapted to be separately driven via electric motors and transmissions, the travelling speed and direction being adjustable separately and jointly. One or several chargeable storage batteries are employed as power supply means. The use of corresponding crawler units offers greater mobility to the wheelchair user than the use of an elevator or escalator which is always stationary, i.e. which requires stairs or buildings; moreover, any later provision of such an elevator or escalator in existing buildings always poses problems. Since in most cases only short distances are being travelled by means of the crawler unit, it may be of light structure, and the travelling speed which can be achieved is not critical. Also, the crawler unit can be taken along in a motor vehicle.
In a known crawler unit of the specified kind, the entire adapter is mounted on the undercarriage for pivoting movement about a transverse axis and can be fixed in various positions of rotation. The back rest of the wheelchair is driven towards the adapter, which is located approximately vertically, and is connected to the adapter via clamps or the like. Due to a corresponding arrangement of the tilting axis, it is possible by tilting the adapter with the wheelchair secured thereto that the wheels of the wheelchair in the tilted state are lifted off the ground, so that the wheelchair is only supported by the crawler unit via the adapter. Preferably, the adapter is extended beyond the back rest approximately to head level of the wheelchair user and is provided with handles by means of which it can be swivelled, there being also provided in the vicinity of these handles control elements for activating and deactivating the drive motors and for controlling the drive speed. Tilting of the wheelchair is necessary so that the seat of the wheelchair will not tilt forwards during climbing of stairs or any other major inclination. Irrespective of whether the assembly travels upstairs or downstairs, the wheelchair user always looks down the stairs. The known crawler unit can only be coupled to the wheelchair by a helper, and it is basically intended that such a helper actuates and controls the unit. Thus, the wheelchair user basically depends on others as regards the use of the crawler unit. The helper is also confronted with problems concerning steering of the crawler unit, because the same rests on the ground during the steering process and to steer the helper has to stand behind the titled wheelchair so as to be able to manipulate the controls. For negotiating narrow staircases or staircases with small landings the use of the known crawler units is frequently impossible for the specified reasons.